The invention relates to a process and apparatus for testing bottles, in particular plastic bottles, conveyed along a conveyor line, for the presence of contamination, by testing gas samples taken from individual bottles.
For returnable bottles, in particular plastic bottles, such as PET bottles, which cannot be washed at high temperatures, the problem arises that contamination needs to be reliably detected so that contaminated bottles can be removed and not refilled. In particular it must be possible to detect returned bottles which a user has used for potentially hazardous substances (poisons, solvents, etc). An already known procedure is to take a gas sample from each bottle and to analyse the sample by photoionization detection (PID). This enables undesired substances present even in small traces in the bottle and/or in the plastic material to be detected. As such testing devices need to have a high throughput of bottles per minute (say 250 to 300 bottles per minute) to enable this kind of testing to be undertaken in an industrial bottling plant, a large number of individual PID units have hitherto been used in parallel in a given bottling line, with each of a corresponding number of bottles to be tested having an individual PID unit assigned to it. This involves high costs in terms of money and maintenance and calibration time.